An electric motor is a device which converts electrical energy to kinetic energy. An electric motor may be generally classified as DC motor or AC motor, inner-rotor type or outer-rotor type based on positional relationship of a stator and a rotor, and winding-field type or permanent-magnet type. Either classification includes an electric motor which utilizes so-called revolving-field, in which a stator revolves field direction to influence a rotor to rotate.
In a revolving-field motor constructed with a stator including a cylindrical coil cylindrically formed by windings and a rotor sandwiching the cylindrical coil and forming air gap, it is well-known that heat is generated by resistance (copper loss) of the cylindrical coil consisting of windings, eddy current at an inner yoke and an outer yoke of a conductor forming the cylindrical coil consisting of windings and the air gap, and hysteresis of an iron core. It is also well-known that copper loss or hysteresis loss which converts magnetic energy to thermal energy is an inevitable technical problem.
To address influence to output and/or efficiency of an electric motor induced by the above technical problem and heat-induced deterioration of coercive force of permanent magnets equipped on an outer surface of an inner yoke and/or on an inner surface of an outer yoke which configure a rotor, it has been attempted to cool coiled surface consisting of windings, such as by feeding cooling air and/or taking in ambient air inside the electric motor, but it does not yet lead to fundamental solution. It is because there are limitations in using a coil or cylindrical coil consisting of windings turned for a number of layers. For example, it is because even if ambient air is taken in to be flowed through a surface of the coil consisting of windings turned for a number of layers, it is technically impossible to feed the cooling air so as to be reached inside of the coil consisting of windings which has heat accumulated.
The present invention relates to a coreless rotating electrical machine which is developed in challenging such technical problem. More specifically, it is characterized in that the present invention is a coreless rotating electrical machine which uses an energizeable coreless cylindrical coil formed of a cylindrical shape having a laminate structure consisting of conductive metal sheets with a plurality of linear parts being spaced in a longitudinal direction, in such a manner that each linear part of the conductive sheets is covered by an insulating layer. In fact, thickness of the laminate structure consisting of two-layer or four-layer conductive metal sheets is only 5 mm, and if both surfaces of a cylindrical coil consisting of such conductive metal sheet laminate can be directly cooled, heat generation control of the coil is possible. The present invention is developed focusing attention on such respect.
Also the present invention relates to a coreless rotating electrical machine configured as comprising, a stator having a cylindrical coil consisting of such laminate of conductive metal sheets, and a lid-type mount which fixes one of end faces of the cylindrical coil; and a rotor having a cup-type mount opposingly positioned with respect to the lid-type mount of the corresponding rotor, with an air gap formed by a bottom, an inner cylindrical air-channel forming body and an outer cylindrical air-channel forming body, in which the cylindrical coil is arranged, and a plurality of magnets equipped on the outer cylindrical air-channel forming body and/or the inner cylindrical air-channel forming body, and a second air space positioned in an inner side and a third air space positioned in an outer side, of the cylindrical coil are formed between open end faces of the cup-type mount and the lid-type mount, wherein the cup-type mount has intake holes leading to the second air space on the bottom and a plurality of exhaust holes leading to the air gap, positioned in a row around a circumference of the outer cylindrical air-channel forming body, close to the bottom and/or a plurality of exhaust holes leading to the air gap, consisting of arrays in a lengthwise direction of the air gap, from the open end face to the bottom on the circumference of the outer cylindrical air-channel forming body with equally spaced intervals.
The coreless rotating electrical machine of the present invention and its cooling method has features as in the followings. Specifically, when the cylindrical coil is energized, the rotor is operated. Differential pressure is generated around the rotor by rotation thereof. With such differential pressure, ambient air is taken into the second air space via the intake holes. At the same time, ambient air is taken into the outer side of the cylindrical coil in the air gap also from the third air space. The ambient air taken into the second air space flows through the inner side of the cylindrical coil arranged in the air gap to cool an inner surface of the cylindrical coil. Similarly, the ambient air taken into the outer side of the cylindrical coil flows through the outer side of the cylindrical coil to cool an outer surface of the cylindrical coil. As a result, the ambient air which has taken therein directly cools a plurality of the magnets exposed in the air gap and both surfaces of the cylindrical coil arranged in the air gap, and the ambient air which has flowed therethrough is discharged from exhaust holes of the rotating outer cylindrical air-channel forming body.
Patent Document 1 (Japanese Laid-Open Patent Publication 2012-016218A) or Patent Document 2 (Japanese Laid-Open Patent Publication 2012-030786A) describes a wheel-in motor using an energizable coreless cylindrical coil. First, Patent Document 1 does not at all describe for cooling heat generated when an electric motor is operated. Also, it is not what considers such respect. On the other hand, Patent Document 2 describes as that, a braking means fixed to an inner yoke in a space formed in an inner surface of the inner yoke of a rotor is further included, and shows a vent hole for communicating the space formed in the inner surface of the inner yoke with ambient air by opening an end face of a wheel fixed to an outer yoke to a stator, and thus, ambient air is taken in from the vent hole to allow for cooling inside of a wheel-in motor, but it is considered that it is for making frictional heat caused by the braking means escape. Both of them are related to the wheel-in motor which has no relationship with the coreless rotating electrical machine of the present invention and its cooling method.
Patent Document 3 (Japanese Patent No. 2,657,192B) describes a linear DC brushless motor, wherein an air supply channel is drilled in a fixed armature, and is “configured to directly blow air from the air supply channel to the armature coil to cool the armature coil as well as to cool a stator yoke itself with respect to a magnet yoke”. However, as described in the above, since it is configured by a plurality of stator yokes attached in parallel to a printed wiring board in moving direction of a slider, with an air-core coil, formed by winding a lead wire for a number of layers, cooling air cannot be blown into interior of the coil formed by winding a lead wire for a number of layers even by directly blowing air to the armature coil. This is obviously not a revolving-field motor which is the subject of the invention.
Patent Document 4 (Japanese Laid-Open Patent Publication 2006-246678A) describes an outer-rotor type wheel-in motor. The electric motor is a SR motor configured with 6 salient poles on a stator side and 4 salient poles on a rotor side provided on a hollow shaft, and Patent Document 4 describes a cooling method for a coil formed by winding a lead wire for a number of layers which is mounted on the 6 salient poles on the stator side in the SR motor. In the cooling method, an inflow channel and an exhaust channel are provided in the hollow shaft via a bulkhead, air is flowed through on a coil surface, and then discharged outside of a stator, and since the air flows only on an exposed surface of the lead wire which is wound for a number of layers, heat accumulated inside the coil formed by winding a lead wire cannot be cooled.
Patent Document 5 (Japanese Patent No. 3,494,056B) describes an outer rotor type magnetic generator configured by a stator with a coil, formed by winding a lead wire for a number of layers, wound around an annular stator core and a rotor consisting of an outer yoke with permanent magnets being supported on an inner surface of a cylindrical part which covers an outer periphery of the stator. There is described a cooling method in which, in the electric motor, a vent hole is provided on a plate which supports the stator rotatably coupled to the rotating shaft, the vent hole on the plate is communicated with a vent hole provided on a bottom of a rotor for cooling a surface of a coil, formed by winding a lead wire for a number of layers, wound around a stator core and the permanent magnets, the rotor is rotated so that air is taken in from the vent hole on the plate and is discharged from the vent hole of the rotor, and the discharged air is further blown to the cylindrical part of the rotor for cooling the surface of the coil and the permanent magnets. In addition, there is described that cooling air is drawn from outside to a rotor yoke, and the cooling air is blown to an outer periphery of the rotor yoke to allow for improving cooling effect to magnets arranged inside of the rotor yoke. However, heat accumulated inside the coil formed by winding a lead wire for a number of layers cannot be cooled even with such outer rotor type magnetic generator.
Patent Document 6 (Japanese Laid-Open Utility Model Publication H5-022133A) describes a method for forcibly cooling interior of an outer rotor type wheel-in motor for an electric vehicle, and a coil used for the electric motor is a coil formed by winding a lead wire for a number of layers, similar to what are described in Cited References 3 to 5, and heat accumulated inside the coil cannot be cooled even if cooling air is fed by a cooling fan.
Patent Document 7 (Japanese Patent No. 2,831,348B) describes an electromagnetic conversion machine configured to supply cooling gas medium into a housing, but the supplying of cooling gas medium into the housing is forcibly performed by a blower. It is described that, in the housing, a rotor is rotated with respect to an armature which forms a coil body. The armature is formed by winding a lead wire, which is covered by an insulating material, for a number of times, and heat accumulated inside the armature cannot be cooled even if cooling air is fed therein.
Patent Document 8 (Japanese Patent No. 3,704,044B) describes a blushless motor using an energizable coreless cylindrical coil formed of a cylindrical shape having a laminate structure consisting of conductive metal sheets with a plurality of linear parts being spaced in a longitudinal direction, in such a manner that each linear part of the conductive metal sheets is covered by an insulating layer, but a cylindrical coil arranged as suspended in an air gap and/or a method or means for cooling a plurality of exposed magnets are not at all considered, and there is no description regarding such respects. It relates to the blushless motor which has no relationship with the coreless rotating electrical machine of the present invention and its cooling method.